120 lines
3.3 KiB
Go
120 lines
3.3 KiB
Go
package alerting
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import (
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"context"
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"fmt"
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"math/rand"
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"sync"
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"testing"
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"time"
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"github.com/benbjohnson/clock"
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"github.com/stretchr/testify/require"
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)
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func TestTicker(t *testing.T) {
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readChanOrFail := func(t *testing.T, ctx context.Context, c chan time.Time) time.Time {
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t.Helper()
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select {
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case tick := <-c:
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return tick
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case <-ctx.Done():
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require.Failf(t, fmt.Sprintf("%v", ctx.Err()), "timeout reading the channel")
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default:
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require.Failf(t, "channel is empty but it should have a tick", "")
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}
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return time.Time{}
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}
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t.Run("should not drop ticks", func(t *testing.T) {
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clk := clock.NewMock()
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intervalSec := rand.Int63n(100) + 10
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interval := time.Duration(intervalSec) * time.Second
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last := clk.Now()
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ticker := NewTicker(last, 0, clk, intervalSec)
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ticks := rand.Intn(9) + 1
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jitter := rand.Int63n(int64(interval) - 1)
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clk.Add(time.Duration(ticks)*interval + time.Duration(jitter))
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w := sync.WaitGroup{}
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w.Add(1)
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regTicks := make([]time.Time, 0, ticks)
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go func() {
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for timestamp := range ticker.C {
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regTicks = append(regTicks, timestamp)
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if len(regTicks) == ticks {
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w.Done()
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}
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}
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}()
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w.Wait()
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require.Len(t, regTicks, ticks)
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t.Run("ticks should monotonically increase", func(t *testing.T) {
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for i := 1; i < len(regTicks); i++ {
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previous := regTicks[i-1]
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current := regTicks[i]
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require.Equal(t, interval, current.Sub(previous))
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}
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})
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})
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t.Run("should not put anything to channel until it's time", func(t *testing.T) {
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clk := clock.NewMock()
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intervalSec := rand.Int63n(9) + 1
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interval := time.Duration(intervalSec) * time.Second
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last := clk.Now()
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ticker := NewTicker(last, 0, clk, intervalSec)
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expectedTick := clk.Now().Add(interval)
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for {
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require.Empty(t, ticker.C)
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clk.Add(time.Duration(rand.Int31n(500)+100) * time.Millisecond)
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if clk.Now().After(expectedTick) {
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break
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}
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}
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ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
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t.Cleanup(func() {
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cancel()
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})
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actual := readChanOrFail(t, ctx, ticker.C)
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require.Equal(t, expectedTick, actual)
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})
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t.Run("should put the tick in the channel immediately if it is behind", func(t *testing.T) {
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clk := clock.NewMock()
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intervalSec := rand.Int63n(9) + 1
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interval := time.Duration(intervalSec) * time.Second
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last := clk.Now()
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ticker := NewTicker(last, 0, clk, intervalSec)
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// We can expect the first tick to be at a consistent interval. Take a snapshot of the clock now, before we advance it.
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expectedTick := clk.Now().Add(interval)
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require.Empty(t, ticker.C)
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clk.Add(interval) // advance the clock by the interval to make the ticker tick the first time.
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clk.Add(interval) // advance the clock by the interval to make the ticker tick the second time.
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ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
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t.Cleanup(func() {
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cancel()
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})
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// Irregardless of wall time, the first tick should be initial clock + interval.
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actual1 := readChanOrFail(t, ctx, ticker.C)
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require.Equal(t, expectedTick, actual1)
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var actual2 time.Time
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require.Eventually(t, func() bool {
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actual2 = readChanOrFail(t, ctx, ticker.C)
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return true
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}, time.Second, 10*time.Millisecond)
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// Similarly, the second tick should be last tick + interval irregardless of wall time.
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require.Equal(t, expectedTick.Add(interval), actual2)
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})
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}
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